The new API includes QAM data, but I've just fallen victim to Comcast encrypting my clear QAM, so I can not test the new MythTV JSON grabber I wrote to confirm that it actually works.

If you still have QAM, either because Comcast hasn't gotten around to you yet, or because you have a QAM-friendly provider, and you're willing to run beta code (preferably on a spare machine so that we don't break your setup), then please send me a message.